RIGHTS groups have slammed the "absurd" exoneration of Egyptian police in the killing of 27 Sudanese refugees in Cairo, calling on the second anniversary of the deaths for a new investigation.

The five groups, including Amnesty International and Human Rights Watch (HRW), said in a joint statement there had been a "concerted effort to absolve the police of any wrongdoing" after security forces assaulted the refugees" makeshift camp on December 30, 2005.

Thousands of riot police wielding batons and using water cannon stormed the protest camp near the offices of the UN refugee agency, leaving at least 27 Sudanese dead – including 11 children and eight women – and hundreds injured.

The protesters were demanding resettlement in a third country, complaining of harsh living conditions in Egypt and discrimination against them.

An official probe into the incident concluded that the deaths resulted from a "stampede".

A memorandum signed by Prosecutor Wael Hussein reveals "serious failures" in the probe, including how public prosecutors and state forensic doctors "collaborated to absolve the police from any responsibility", the statement said.

Of the more than 100 police officers interviewed, none could say who issued the order to storm the camp, it added.

Despite arresting hundreds of Sudanese refugees in the wake of the assault, investigators interviewed only one woman survivor among them, as well as four other eyewitnesses who said the protesters themselves initiated the violence.

Justice ministry forensic doctors said that serious head injuries led to many of the deaths but claimed there was "a lack of any signs indicating the use of excessive force in assaulting them".

As a result, prosecutors did not charge any police but instead charged the protesters en masse with manslaughter, resisting the authorities and the deliberate destruction of property.

"Charging the protesters with serious crimes and exonerating the police of any wrongdoing is the absurd but inevitable outcome of a sham investigation," said Hossam Bahgat, director of the Egyptian Initiative for Personal Rights.

A United Nations human rights panel in April called on Egypt to reopen the investigation into the deaths, saying it had been closed without clarifying the circumstances leading to the deaths.

The UN committee on the protection of the rights of migrant workers in Geneva also called for the probe to be reopened "in order to clarify the circumstances leading to the deaths of the Sudanese migrants".

The rights groups called on President Hosni Mubarak to use the second anniversary to open an independent investigation into the killings.

"President Mubarak should use the second anniversary of the police action against Sudanese protesters to initiate a complete and transparent investigation of what really took place," said HRW"s Joe Stork.

"The public prosecutor"s total exoneration of the police lacks any semblance of credibility."